Morality is definitely my favourite area of philosophy. And being a philosophical point of argument there are also very different views that you can take. Mai'dah raises an interesting point, for instance, about there always being a scenario where killing is unjustified. An absolutist pacifist, for example, would never be alright with killing, even in a video game.
Justin also raises an interesting point of moral killing being in self-defence. Pretty much every legal system across the world and every major religion recognizes the right to self-defence as being legitimate. An example of this is Christianity, where Jesus Christ recognizes someone's right to raise the sword in self-defence. (But being an absolutist pacifist, Jesus then waves this right during his arrest, when he tells Peter, the apostle, to stand down.)
Finally, Greg takes the judicial (also: Kantian) approach to morality, whereby as long as you stay within the confines of what is perceived to be moral in "real life", everything that falls outside that is alright (i.e. killing fictional characters). However, one thing about Kantian philosophy is that it assumes a free will, which comes under fire from more-modern psychological theories.
Greg assumes that you have a choice between killing in real life and killing in video games, but psychological theories add a new dimension to the debate. If, for instance, we would find ourselves in an apocalyptic scenario where laws against killing can't be enforced, the people who are more adjusted to killing people in video games, might find themselves acting more like a Daryl than a Herschel, despite the fact that we can all consciously distinguish between real life and fiction.
